This invention relates to a pressure responsive actuator device and particularly one which operates automatically in response to a reduction in fluid pressure which surrounds it within a confined space.
In various types of apparatus and devices it is necessary to detect a drop in pressure within a confined space and provide a signal or indication of the pressure drop. For example, in vehicle tires which are normally inflated to a predetermined pressure, it is desirable to sense when that pressure decreases due to the development of a leak in the tire. In such an application it is also desirable to provide a pressure sensor that requires a minimum of calibration. Heretofore, pressure responsive actuators utilized diaphragms, springs and other mechanical parts yieldable to pressure. Considerable manufacturing precision and close tolerances were required for such parts in order to calibrate the sensor for use at certain pressure levels. This often contributed to an excessive unit cost or a lower level of reliability. For example, one common form of pressure responsive switch utilized a spring biased piston in a chamber, the piston being forced by the spring to move and close electrical contacts when pressure in the chamber was reduced. Such an arrangement required a multiplicity of precision made parts in order to provide an acceptable level of reliability and accuracy. In view of these difficulties a need arose for an improved actuator of greater simplicity and reliability